CHAPTER 22

Turing’s Zeitgeist

brian e. carpenter and robert w. doran

T

his chapter reviews the history of Alan Turing’s design proposal for an Automatic

Computing Engine (ACE) and how he came to write it in 1945, and takes a fresh look

at the numerous formative ideas it included. All of these ideas resurfaced in the young

computing industry over the following fifteen years. We cannot tell to what extent Turing’s

unpublished foresights were passed on to other pioneers, or to what extent they were redis-

covered independently as their time came. In any case, they all became part of the Zeitgeist

of the computing industry.

Introduction

At some universities, such as ours in New Zealand, the main computer in 1975 was a Burroughs

B6700, a ‘stack’ machine. In this kind of machine, data, including items such as the return

address for a subroutine, are stored on top of one another so that the last one in becomes the

first one out. In effect, each new item on the stack ‘buries’ the previous one. Apart from the old

English Electric KDF9, and the recently introduced Digital Equipment Corporation PDP-11,

stack machines were unusual. Where had this idea come from? It just seemed to be part of

computing’s Zeitgeist, the intellectual climate of the discipline, and it remains so to this day.

Computer history was largely American in the 1970s—the computer was called the von

Neumann machine and everybody knew about the early American machines such as ENIAC

and EDVAC. Early British computers were viewed as a footnote; the fact that the first stored

program in history ran in Manchester was largely overlooked, which is probably why the word

‘program’ is usually spelt in the American way.^1 There was a tendency to assume that all the

main ideas in computing, such as the idea of a stack, had originated in the United States.

At that time, Alan Turing was known as a theoretician and for his work on artificial intel-

ligence. The world didn’t know that he was a cryptanalyst, didn’t know that he tinkered with

electronics, didn’t know that he designed a computer, and didn’t know that he was gay. He was

hardly mentioned in the history of practical computing.

There were clues. The first paper published on the ACE did say ‘based on an earlier design

by A M Turing’.^2 A trade press article by Rex Malik^3 described Turing as ‘a four in the morning